Re: [PATCH 2/3] mm: make the threshold of enabling THP configurable

[Cong Wang <amwang@redhat.com>]

于 2011年06月22日 19:15, Mel Gorman 写道:
> On Wed, Jun 22, 2011 at 06:46:39PM +0800, Cong Wang wrote:
>> ??? 2011???06???22??? 17:16, Mel Gorman ??????:
>>>
>>> What I meant was that there is a rational reason why 512M is the
>>> default for enabling THP by default. Tuning it lower than that by any
>>> means makes very little sense. Tuning it higher might make some sense
>>> but it is more likely that THP would simply be disabled via sysctl. I
>>> see very little advantage to introducing this Kconfig option other
>>> than as a source of confusion when running make oldconfig.
>>>
>>
>> The tunable range is (512, 8192), so 512M is the minimum.
>>
>> Sure, I knew it can be disabled via /sys, actually we can do even
>> more in user-space, that is totally move the 512M check out of kernel,
>> why we didn't?
>>
>
> Because the reason why 512M is the default is not obvious and there
> was no guarantee all distros would chose a reasonable default for
> an init script (or know that an init script was even necessary).
> This is one of the few cases where there is a sensible default that
> is the least surprising.
>

Putting a well-explained Kconfig help would solve this problem,
so I don't think this is a surprising thing.